please help mhe.. cari x nya e

Materi : Matriks
Bahasan : Determinan Matriks
Jawaban : x = - 4 atau x = 3

Langkah - langkah :
[tex]a = \left[\begin{array}{ccc}a&b\\c&d\end{array}\right] \\ \\ |a| = ad - bc[/tex]
|a| = (3x(5 + x)) - 5x
|a| = 3x² + 15x - 5x
|a| = 3x² + 10x

|b| = 36 - (- 7x)
|b| = 36 + 7x

|a| = |b|
3x² + 10x = 36 + 7x
3x² + 3x - 36 = 0
x² + x - 12 = 0
(x + 4) (x - 3) = 0
x = - 4 atau x = 3